They look like the small magnets so 37 isn't really that insane. It would be relatively easy to swallow them, I would think.
Also kids eat all sorts of crap when no one is looking. I chewed off part of a plastic cup and swallowed it. My sister swallowed a house key when my mom turned around for just a few seconds. She turned back around and the key was gone, but my sister had a smirk on her face. It's not necessarily negligence, but it does highlight the need for children to be supervised and be in a child-safe environment. Most parents do the best they can, I presume.
I dunno, 37 sounds like quite a lot to me, looking it up real quick I would guess the magnets were from a office toy like this:
Which, really, small stuff like that you should just know
to keep out of the reach of small children and not take any chances, placing this one shelf-higher could have done a lot to prevent this girl's injury and possible death.